1. Field of the Invention
The present invention relates to an improvement in the structure and method of assembling a sleeping bag.
2. The Prior Art
A sleeping bag structure is known, wherein the outside material and the lining form a space therebetween to be filled with a large quantity of feathers. Certainly, such a feather-filled sleeping bag is advantageous in certain aspects such as its ideal heat insulating effect and portability. However, it also has serious disadvantages such as its high cost and the fact that the feathers tend to bunch up within the sleeping bag structure, often adversely affecting the heat insulating effect.
Feathers are generally high in their moisture absorption characteristics and thus have their volume reduced as they absorb moisture. Such tendency causes a mass of feathers to become further bunched up in the sleeping bag structure and even after dried and redistributed within the sleeping bag, feathers can never be restored to their initial uniform distribution within the sleeping bag structure. This also adversely affects the heat insulating effect.
It has also been known that, after the space between the outside material and the lining has been filled with a layer of feathers, the sleeping bag may be subjected to a quilting operation performed through the outside material, the feather layer and the lining so as to clamp the feather layer against displacement thereof within the bag structure. However, such quilting disadvantageously prevents the feather layer from conforming to the configuration of a human body and deteriorates the heat insulating effect at least in the region of quilting. Thus, the most preferred characteristics of the high cost feather filler material cannot be adequately enjoyed.
Attempts have been made to solve the above-described problems. In one proposed solution, the structure of a sleeping bag is formed so that a layer of synthetic fiber or cotton and a thin layer of feathers are formed between the outside material and the lining and directly sewn together therewith. Such an improvement permits the ideal characteristics of feathers to be satisfactorily enjoyed by the user. The layer of feathers can be held to some degree against being bunched up against the layer of synthetic fibre cotton during use of the sleeping bag and the sleeping bag can be provided at a relatively low cost. However, even in this improved structure, the layer of feathers still bunches up to some extent and the problem of heat insulation remains unsolved.
In another proposed solution, the sleeping bag structure comprises an outside material, a lining and partition sheets interposed between the outside material and the lining in such a manner that the individual partition sheets are sewn along their upper and lower edges to the outside material and the lining material, respectively, to form a plurality of tubular spaces defined by the outside material, the lining and an associated pair of partition sheets, to be filled with respective portions of a feather layer together with respective portions of another heat insulating layer. In this prior art structure, however, it has been extremely difficult to fill the tubular spaces with the feather layer together with the other heat insulating layer. Consequently, the assembly of such sleeping bags has been extremely time consuming and cumbersome.